The present invention relates generally to a brake mechanism for motors or the like, and more particularly to spring set, magnetically released brakes in which a rotatable disc secured to a shaft is clamped by spring pressure between two non-rotating surfaces to effect a braking action that prevents or stops angular motion of the shaft. Braking action clamping pressure is disabled and released by energizing an electromagnetic device, such as a solenoid, which usually occurs at the moment power is applied to the driving motor. The plunger of the solenoid pulls against a simple lever mechanism which overcomes the spring clamping pressure and allows the disc and shaft to rotate.
Brakes of this type are common in the power transmission industry and a study of the state of the art reveals that most all employ the same general principles. A number of prior art references point out the use of solenoid plunger motion to overcome spring pressure directly without the aid of a mechanical advantage. Such implementation requires employment of large solenoid coils and brings about problems relating to space, weight, heat, cost, and the like.
Other inventions resort to the use of complex systems of gears, cams and/or linkages to gain high mechanical advantages and thus permit the use of smaller solenoid coils. Obtaining a high mechanical advantage is not without some disadvantage, however, in that reactive, reverse direction forces require the action of gravity to return the solenoid plunger to a de-energized position As a result, there is imposed a severe restriction on orientation of the brake when mounted on a frame or motor. These structures inherently necessitate the use of a greater number of parts that are subject to wear, failure and frequent adJustment. In addition, because of the complex arrangement of assembled components, these and other parts are more difficult to replace after Wear or failure. In addition, as these parts wear, they become illfitted and more prone to backlash, rattle and production of objectionable noise
Various attempts to solve the problems of the prior art have been made and are illustrated in a number of U.S. patents, including U.S. Pat. Nos. 3,500,971; 3,525,424; and 3,556,266. In addition, U.S. Pat. No. 4,181,201 owned by the assignee of the present invention discloses a brake mechanism wherein a solenoid is mounted o a support lever that is connected to a cam pivoted to a end plate and adapted to contact the support lever near its free end to overcome the force of a spring and release the brake when the solenoid is energized. The arrangement of the many parts provides a solenoid mechanical advantage in the neighborhood of 24-32 to 1. The spring mechanical advantage varies considerably from the ratio of the present invention and is in the order of 81/2 to 1.